I have a VT leaflet here which describes the train shop as "self service" - does this mean there is a special system for paying like self service checkouts in supermarkets or is there a member of the train crew in there taking money?

Yeah.. that wording tricked me before the Pendolino's were introduced- I assume the term "self service" is used in relation to the fact that on traditional buffets, you simply asked the person serving you for the requested item from the buffet- as apposed to on Voyagers/ Super Voyagers/Pendolino's, where you take your item to the till point (or EPOS), where the CSA will scan it & take your money.

On the subject of on-board food/drink facilities:
I've always been curious as to why most TOCs havn't installed vending machines on their vehicles. Although there wouldn't be much point on units with shop/buffet facilities like Pendos, on other trains - Especially shorter interurban and suburban services which often don't have buffets or trolleys on board - This would be a very welcome addition, especially as there is rarely enough time at a station call to use the shops or machines on the platform!

After all...If JR, NSB, DB and other countries can do it, there's stuff-all reason why we can't!